BIOL 2P93 Lecture Notes - Lecture 23: Archegonium, Pollen Tube, Pollination
24 Jan 2016
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: pollen grains have 2 prothallial cells, small generative cell + tube cell. Female half: ovulate pine cones larger + complex than microsporangiate (male) cones: Ovuliferous scales (cone scales) bear ovules are not just megasporophylls, they"re modified determinate branch systems (seed-scale complexes) consists of ovuliferous scale (bears 2 ovules on upper surface) + subtending sterile bract (bract extends under scale to support it). Helical arrangement of ovuliferous scales along cone axis. Ovulate pine cones, indicating larger relative sizes compared to mature microsporangiate cones. e) white pine and f) red pine. Longitudinal section of young ovulate cone of pinus sp. Note arrangement of ovuliferous scales along axis of cone. Longitudinal section of ovulate pine cone showing seed-scale complex, w/ ovuliferous scale + sterile bract. Ovule w/ single megasporocyte (megaspore mother cell) surrounded by nucleus/megasporagium + integument. Sterile bract considered to be morphologically = to leaf. Ovulate cones compound, microsporangiate cones simple (microsporangia attached to microsporophylls).
